The present invention relates to improvements in disc brakes of the kind including a stationary member adapted to be secured to a non-rotatable part of a vehicle, a caliper member supported on the stationary member so as to move toward and away from a rotatable disc, and a pin and guide bore device provided between the two members to guide the movement of the caliper member with respect to the stationary member.
The disc brakes of the aforementioned kind further include a pair of friction pads disposed on opposite sides of the rotatable disc, and an actuator such as a hydraulic piston and cylinder device, incorporated in the caliper member to directly act on one friction pad or a friction pad on the piston side, thereby pressing the same against one surface of the disc. The other friction pad is applied against the other surface of the disc by the reaction force generated in the actuator.
The one friction pad, such as the friction pad on the piston side, is usually supported on the stationary member to move toward and away from the disc, while the other friction pad may also be mounted on the stationary member or may be mounted on the caliper member. For mounting the friction pad on the stationary member, a pair of opposing and circumferentially projecting lugs is formed on the friction pad, and the lugs are slidably supported on axially extending and circumferentially spaced stepped portions formed on the stationary member. The pin and guide bore device usually comprises a pair of circumferentially spaced parallel guide bores formed in the stationary member and slidably receiving therein pins which are secured to the caliper.
Disc brakes having such a construction generally operate satisfactorily. However, there are shortcomings such that the friction pad on the side of the piston and supported on the stepped portions of the stationary member sometimes moves off the stepped portion of the stationary member in the direction away from the surface of the disc when the piston or the caliper has accidentally been displaced beyond the normal operating range, whereby the friction pad may drop out of the disc brake.